ND vs. Beam Old Grandad question

I purchased several bottles of Old Grand Dad (86 proof) with ND stamps on the "large" cap (bottles stamped with 86 on the bottom) and love it. Everything I have read says Beam uses the same mashbill and yeast strain as National Distillers. My problem is that they don't taste anything alike and I have tried several different bottles of each. The Beam product seems to me to taste more like JB White (funky "yeast" taste) than the ND OGD. My question is why the difference. Do they really use the old mashbill and yeast? Are they aged the same? and/or Does sitting on a shelf for 25 years affect the taste of the bourbon?

And in that "strain" of thought: How do distilleries that use more than one yeast strain prevent cross contamination?

Re: ND vs. Beam Old Grandad question

If I had to guess what would be the biggest thing causing it to taste different, it would have to be the proof off of the still. Then followed by barrel proof. The nd was probably a lot lower proof off of the still, and therefore had more flavor in it. I agree, there is a huge difference in the 2.

Re: ND vs. Beam Old Grandad question

Different distillery, different stills. Other differences in standard processes and procedures. I know next to nothing about the inner workings of the Old Grand-Distillery at Forks of the Elkorn, so who knows what changed? I just know that the mashbill and yeast strain did not. Those were retained.

Re: ND vs. Beam Old Grandad question

Craig is right about age. Most of the ND OGD people have today is glut-era whiskey and probably significantly older than expected, e.g., NAS bottlings typically being 8 to 10 years old instead of the 4 to 6 you'd expect, which is probably what we're getting now, if that.